mathew has saved 50 dollars and each week he increases his savings by 5 dollars. his brother mark has 35 dollars saved and each week he saves an additional 7 dollars. how long will it take for mark to have more money than matthew?
mathew: amount = 50 + 5w
brother: amount = 35 + 7w
when is 35 + 7w = 50 + 5w ?